Almost every roofed structure is provided with some protective covering for the roof, and various types of roofing have been widely used for a long time. Examples of these are tiles, shingles, rocks, asphalt sheets, etc. Several factors must be considered when choosing a particular type of roofing. Obviously, perhaps the most important function of roofing is to protect the underlying structure from the effects of the weather. When the roof is covered by a pattern of overlapping elements such as shingles, not only must each individual element be impervious to the weather, the areas where adjacent shingles overlap and adjoin each other must also provide an effective weather seal.
Other factors are cost, weight, and ease of manufacture and installation. Tiles, for example, usually provide relatively long-life protection, but they are correspondingly expensive and heavy. The greater weight of tiles means, moreover, that not only are they more difficult to install, but in some cases it may even be necessary to strengthen the underlying supporting structure of the roof.
Yet another factor when choosing roofing material is the appearance of the covering. Although it is usually easy to vary the color of the outer surface of the covering, for example by fixing colored granules on it at the time of manufacture, other features are not as easily provided. In particular, the flat and bland appearance of roofs covered with sheeting or common asphalt shingles is often considered less pleasing than the textured appearance of tiled or wood shake roofs.
One type of roof which gives the impression of texture and depth associated with tiled roofs is the shake roof. This roof is made up of a pattern of overlapping, tapered wooden strips which are nailed to the roof like shingles. Although a shake roof is somewhat more expensive and much lighter than a tiled roof, there are several disadvantages associated with the use of wood. Long-term exposure to the environment typically leads to buckling and cracking of the wooden strips, which in turn leads to a corresponding worsening of the protective seal provided by the shake roof. Also, unless specially treated, wooden roofs constitute a much greater fire hazard than roofs covered with other materials.
One attempt at giving a textured profile to a roof covering while using relatively inexpensive asphalt shingles is described in U.S. Pat. No. 3,913,294 (Freiborg). Each shingle in this roofing system exhibits a thickened portion formed by folding the shingle several times so that the folds extend laterally across a central region. The shingles are installed in such a way that the lower edge of each overlying shingle extends over and beyond the thickened portion of its underlying shingle. In this way, the lower edge of each shingle is raised relative to its upper portion, thereby adding depth.
The disadvantage of this shingle is that it is not possible to apply such a technique using multiple, sharp folds or bends to shingles made of stiffer or more brittle materials. In particular, it cannot be used for shingles made of fiber glass, which are more durable than roof coverings made of organic materials such as asphalt and wood, but which tend to crack when bent sharply.
U.S. Pat. No. 2,062,149 (Stark et al.) describes a shingle consisting of an elongated sheet or strip of composite roofing material. In order to create a textured profile, a lath is secured near and parallel to the lower edge of each strip. The lower edge itself is then bent down substantially at a right angle over the lath to form a lip. Bending a portion of the covering strip or shingle sharply over a thickened lower portion of an underlying element in order to form a lip and provide depth is also utilized in U.S. Pat. No. 3,377,762 (Chalmers et al.). In this system, the material which must be bent to form the lip is metal, in particular, aluminum. In both of these systems, part of the covering element must be bent sharply, so that both preclude the advantageous use of materials such as fiber glass.
U.S. Pat. No. 2,394,379 (Herbes) describes an outer wall covering intended to simulate the appearance of clapboard siding. According to this system, elongated wooden battens are first nailed in equally spaced parallel rows to underlying sheathing over the entire height of the wall to be covered. Elongated flat siding boards of asbestos-cement are then nailed in position, whereby the upper edge of each butts against the lower face of the battens of the next upper row and the lower edge bears on and overhangs the battens of the next lower row. First, this covering involves a siding, not a roof cover. Second, it uses asbestos-containing siding boards, so that a dangerous material must be handled upon manufacture. Third, this solution relies on wooden battens, which, as is pointed out above, are prone to relatively rapid deterioration. Finally, the battens in this wall covering are elements separate from the siding boards, and must be handled and installed separately.
A siding structure similar to that found in Herbes, and exhibiting similar limitations and disadvantages, is disclosed in U.S. Pat. No. 2,648,103 (Wahlfield). According to this system, an elongated molding wooden member having a relatively complicated cross section is fastened along the lower edge of each of a number of wooden siding boards. When installed, the upper edge of each siding board mates with a corresponding offset which must be formed in the inner lower edge of the molding member of the siding board in the next higher row. In an alternative embodiment, a metal profile replaces the wooden molding member, whereby the offset is created by bending the profile a number of times at substantially right angles. A wedge-shaped member is additionally required to support the siding boards and to improve their ability to seal out the environment.
Accordingly, the object of the present invention is to provide a roof covering which not only gives the pleasing appearance of a shake roof, but also seals well against the environment, resists bending, and combines durability and affordability with ease of manufacture and installation.